Department of Ophthalmology, Center for Vision Research, SUNY Upstate Medical University, Syracuse, New York 13210.
eNeuro. 2018 Aug 29;5(4). doi: 10.1523/ENEURO.0181-18.2018. eCollection 2018 Jul-Aug.
The mammalian visual system has a remarkable capacity to detect differences in contrast across time, which is known as temporal contrast sensitivity (TCS). Details of the underlying neural mechanisms are rapidly emerging as a result of a series of elegant electrophysiological studies performed largely with the mouse as an experimental model. However, rigorous psychophysical methods are necessary to pair the electrophysiology with temporal visual behavior in mouse. The optomotor response is frequently used as a proxy for retinal temporal processing in rodents. However, subcortical reflexive pathways drive the optomotor response rather than cortical decision-making areas. To address this problem, we have developed an operant behavior assay that measures TCS in behaving mice. Mice were trained to perform a forced-choice visual task and were tested daily on their ability to distinguish flickering from nonflickering overhead lights. Correct responses (Hit and Correct Rejections) were rewarded. Contrast, temporal frequency, and mean illumination of the flicker were the independent variables. We validated and applied the theory of signal detection to estimate the discriminability factor (´), a measure of performance that is independent of response bias and motivation. The empirical contrast threshold was defined as the contrast necessary to elicit ´ = 1 and TCS as the inverse of the contrast threshold. With this approach, we established in the mouse a model of human vision that shares fundamental properties of human temporal psychophysics such as Weber adaptation in response to low temporal frequency flicker and illumination-dependent increases in critical flicker frequency as predicted by the Ferry-Porter law.
哺乳动物视觉系统具有卓越的检测时间上对比度差异的能力，这被称为时间对比敏感度 (TCS)。由于一系列使用小鼠作为实验模型的精巧电生理研究，有关潜在神经机制的细节正在迅速浮现。然而，为了将电生理学与小鼠的时间视觉行为相匹配，严格的心理物理学方法是必要的。光运动反应经常被用作啮齿动物视网膜时间处理的替代物。然而，皮质下反射性通路驱动光运动反应，而不是皮质决策区域。为了解决这个问题，我们开发了一种行为测定法，用于测量行为小鼠的 TCS。小鼠接受训练以执行强制选择视觉任务，并每天接受测试，以测试其区分闪烁和非闪烁顶灯的能力。正确的反应（命中和正确拒绝）会得到奖励。对比度、时间频率和闪烁的平均照度是独立变量。我们验证并应用信号检测理论来估计辨别力因素 (´)，这是一种独立于反应偏差和动机的性能衡量标准。经验对比阈值被定义为引起´= 1 所需的对比度，而 TCS 则是对比度阈值的倒数。通过这种方法，我们在小鼠中建立了一种与人类视觉具有基本相同特性的模型，例如对低时间频率闪烁的韦伯适应，以及根据费里-波特定律预测的临界闪烁频率随照明强度的增加而增加。
